This section provides background information related to the present disclosure which is not necessarily prior art.
Isolated power converters are commonly used to provide electrical isolation between two interrelated systems, such as a power source and an electric load. In many cases, isolated power converters are required to satisfy safety specifications. Thus, isolation must be provided in the power stage and in the control loop of the power converter. Power stage isolation is typically provided using a transformer. Isolation in the feedback control loop is often provided through an opto-coupler (also known as an opto-isolator).
A disadvantage of using opto-couplers is the large unit-to-unit variation in their current transfer ratios (CTRs). The performance of the power supply (including its loop gain) is related to, among other things, the CTR of its opto-coupler. Therefore, the variations in CTR from one opto-coupler to another imposes constraints on control loop design.